Undoubtedly, the most critical component in any mission-critical data center isn’t the capacity of data servers or the types of UPS batteries; it’s the life-safety measures. Smoke, not the flame itself, is the greatest threat to safe evacuation and survival…

It’s well understood that the battery in a UPS is the most vulnerable part of the system. In fact, battery failure is a leading cause of load loss. Knowing how to maintain and manage UPS batteries will extend their life…

The data center industry, facing exponentially growing demand for data and networking capacity, is challenging its power distribution and protection partners to provide electrical infrastructure topology solutions—including uninterruptible power supply (UPS) modules—with a wider range of power reliability to protect against utility or system power anomalies and failures. This level of reliability is being calculated not just in time (hours or days), but also by number of events (measured in “single events over years”). For the typical mission-critical data center, the number of failure events matters as much as the duration of the event.

The mission-critical power industry has responded with a wide range of UPS protection topologies that rely on layers of equipment and power-distribution redundancy. This redundancy certainly provides critical levels of reliability, load sharing and efficiency, but at an escalating capital expense (capex) and operating expense (opex) cost.

These redundant topologies (described later) can, at higher levels, provide reliability that the Uptime Institute[1] estimates at less than one event per year and less than 0.8 hours of downtime per year for a Tier IV data center. But it’s fair to ask questions such as “At what cost?” and “For what kind of data center?” or simply “How can we right-size the critical power system to match the function of our data center?”

Right-Sizing Redundancy and Reliability

As the data center market diversifies, some segments and applications will require very little critical power protection (e.g., Uptime Institute Tier I data centers that handle cloud computing for social media or search engines). Others, such as colocation data centers with service-level agreements (SLAs) of 100 percent uptime, video streaming, e-commerce and financial/stock trading strive for Tier III/IV ratings for their mission-critical applications. There also are a range of data center applications in the middle of this tier ranking (Tier II/III) with varying requirements for uptime and reliability.

Each of these Uptime Tier rankings requires a different level of redundancy that must be delivered by the UPS system topology. Each of these topologies can be implemented in several different configurations. The selection of the optimal UPS system depends on important factors including redundancy, load power (in kilowatts, or kW), fault isolation, load sharing, asset utilization, capacity scaling and total cost of ownership (TCO) measured in capex and opex.

The N System Topology

The N system is the most basic critical power-distribution topology, where “N” is the load capacity measured in kW. These systems do not place UPS modules in parallel (or redundant) positions, thereby decreasing system reliability.

Figure 1: N system topology.

This system topology also has multiple “single” points of failure, with failure events of one to two per year,[2] which makes it the least reliable. A single point of failure is defined as part of a system that, if it fails, will stop the entire system from working. For reference, the typical U.S. utility electrical grid averages 24 failure events[3] outside the ITIC/ CBEMA[4] curve per year. Again, for certain low-risk applications, such as internal information technology (IT) processes where failure has no impact on a business or large group of users, this N topology can be very effective.

The main advantage of the N system topology is the low initial acquisition and operational costs (excluding the costs associated with unplanned outages). Another advantage is high utilization rates of the system assets. UPS modules for an N system topology are sized to have a design load of 80 to 90 percent of the full load rating.

The N+1 System Topology

An N+1 system topology begins to add redundant components to improve reliability. “N” is, again, the load capacity and “+1” refers to one additional UPS in the system for redundant power protection. These systems operate UPS modules in a parallel configuration, but they still have multiple single points of failure, including the paralleling bus for the output of the UPS modules. An N+1 system also lacks redundant distribution paths and therefore has some risk of single points of failure with an estimated failure rate of one event per year.

Figure 2: Parallel redundant N+1 system.

This topology has seen widespread adoption for both call centers and colocation data centers with SLAs of less than 100 percent. It is also suitable for any enterprise with a low dependency on delivering Internet-based services.

An N+1 system topology, with fewer redundant elements and higher utilization rates, has low initial costs and low operational costs. Its higher utilization rate depends on the number of UPS modules or generators required for N load. UPS modules for an N load are sized with a design load of 80 to 90 percent of the full load rating with an additional UPS module and generator added to the system. For example, an N+1 system consisting of two UPS modules will have a normal module loading of 40 to 45 percent, whereas an N+1 system consisting of five modules would still be limited to module loading of 65 percent to 70 percent.

The Block-Redundant (Catcher) System Topology

Another variation of this parallel power architecture is the block-redundant system topology, commonly referred to as a catcher system. This approach is an economical way to improve system reliability without having a complete 2N system. It relies on static transfer switches (STS) and the ability of the catcher UPS module to instantly handle a sudden shift, or step load, by shifting the load from the affected UPS to the standby UPS. In most block-redundant implementations, however, the STS is also a single point of failure and, although the UPS module utilization is improved, it is still limited to 70–75 percent loading to ensure redundancy.

Figure 3: Block-redundant (catcher) system.

The Shared Redundant (4N/3) System Topology

A shared redundant 4N/3 system topology is very similar to the block-redundant topology, except the load is spread across multiple paths and all the UPSs are loaded to avoid the block loading of the “catcher” system. The 4N/3 and 3N/2 variations are the most common forms of the shared redundant topology, and the utilization levels of these topologies are in the 60–70 percent range. The shared redundant system designation, such as 3N/2, is the ratio of UPS maximum capacity—(megawatts (MW)—to maximum critical load (MW), so the UPS maximum loading utilization would just be the inverse of 2 MW (load) / 3 MW (UPS), which equals 67 percent efficiency.

Figure 4: Shared redundant 4N/3 system.

As Figure 4 shows, this topology also requires a significant cable and distribution infrastructure, which increases the initial capital and installation costs and makes system scaling more difficult. In addition, the system can have single points of failure in the power distribution on the output of the UPS.

Both the block-redundant and shared redundant systems provide higher reliability than N+1 with estimated failure rates measured at less than one event per year. This performance is well suited to most organizations where real-time delivery of data or applications has no direct or significant impact on service delivery, revenue or even corporate reputation. The challenge with these systems is that the maximum utilization is limited to less than 70–75 percent, and the actual utilization is usually much less owing to limited capability to share loads across this power infrastructure. The UPS and critical power assets for block-redundant or shared redundant systems can become stranded and underutilized because the actual critical load often changes when the systems are deployed, thanks to IT loads/servers being added, removed, upgraded or moved during the life of the data center.

The System Plus System (N+N) Topology

A system plus system (or N+N) topology incorporates two independent and redundant electrical-distribution systems. This topology can be designed with either N components in each system or with N+1 components in each system. The two independent systems provide for concurrent maintainability and, in some designs, can be fault tolerant.

Figure 5: System plus system (S+S).

A system-plus-system topology provides very high levels of reliability, but it also has the highest initial cost and TCO combined with a low asset-utilization rate (40 to 45 percent of maximum design load). The topology is estimated to experience only one to two unplanned outages (load drops) in a five-year period. These designs are generally used in corporate or financial-services settings where high availability—measured in single events per five years—are core to the guaranteed services (such as an SLA for a colocation center), have a significant impact on revenue, or create corporate operational risk or liability.

Summary

The data center industry is dynamic and changing. Shifts in system reliability are required to match data center “mission” and “critical” deliverables. As the evolution of existing UPS system topologies demonstrates, the data center market has a range of systems that can provide optimum levels of high reliability (N+N), but at very high cost. Other options are systems that can reduce cost but with much lower reliability (N or N+1) or systems that provide a middle ground (block or shared redundant), forcing complicated tradeoffs on cost, reliability and utilization. The next challenge for the industry will be to push these boundaries to find new system solutions that provide the right level of redundancy and reliability while driving down both capex and opex and yielding lower TCO.

About the Author

Brad Thrash, product manager in GE’s Critical Power business, is part of a team of dedicated people who work with GE’s data center, communications, computing and content customers that are wrestling with the exponential and insatiable demand for ever increasing capacity. These customers challenge Brad to help them increase data capacity, build better and smarter data infrastructures and improve operational returns. Brad holds a B.S. in mechanical engineering and is a licensed professional engineer. He is a member of the Institute of Electrical and Electronics Engineers (IEEE) and the American Society of Mechanical Engineers (ASME). Brad is also on the Power Sub Work Group of The Green Grid.

[4] Information Technology Industry Council/Computer Business Equipment Manufacturers Association curve is the voltage immunity requirement that assists the critical power in understanding what technical problem the UPS is expected to solve.

The tendency towards mega data centers in the internet and IT sectors requires an increasing demand for stable power at single locations. With more demand for data storage (owing to frequent uploads of photos to Facebook or other social-media accounts), data centers are becoming bigger and consuming larger amounts of power. They are beginning to take on a more industrial approach to power consumption. That said, more and more large, critical industrial processes rely on a power-quality level that the public grid cannot provide. The distribution of the electrical power in many of these large facilities is realized at medium-voltage (MV) level.

Medium-voltage distribution reduces losses and space by a simple reduction in current. As voltages increase, the required current reduces for the same power level. The modular design of a static UPS allows a simple replacement of the grid-to-load interface from low-voltage (LV) to medium-voltage components, keeping the basic parts of the UPS and storage the same as for LV applications. In this way, the proven and familiar experience of working with the function and maintainability of a reliable LV UPS is maintained, but the advantages of medium voltage are achieved.

Advantages of Medium-Voltage UPS Technology

Fast-growing online activity over the last decade has forced a rapid rise in both space and electrical power required to operate data centers. Accordingly, power density becomes higher, and cooling of these data centers becomes critical. Economies of scale mean single data center locations have grown larger, with a demand for a safe power supply reaching well into the tens of megawatts. Integrating a medium-voltage UPS system to protect these critical applications will reduce feeder ampacity. For example, 1 MW in a 400/230 VAC system means 1,443 A of current per phase. If the voltage is 15 kV, the current for 1 MW power is only 115 A. Another feature of the MV UPS is that the system can be centralized, which helps manage floor loading and gives freedom in the floor plan.

One of the major cost issues in a data center or a production facility is efficient use of floor space. Reducing the space for infrastructure equipment results in additional space for IT or manufacturing equipment. Often the available area for the UPS system is limited, particularly in existing buildings, but the required power is increasing. High-power, compact, MV static UPS products are well suited to overcoming this challenge. Modern static MV UPS systems also make extensive use of low-voltage components, including the entire power-electronics, energy-storage and control systems taken from standard and proven low-voltage units.

Besides the footprint, electrical losses are an important point to consider. Particularly at long distribution distances, distribution losses can become significant. For longer distribution lengths, the influence of the cable will rise, so medium voltage will yield a better result.

Typical MV Applications Now Appear in Today’s Economy

In mega data centers, the philosophy is quite similar. Many design options are possible, including performing the UPS function at medium voltage and having MV distributed to the individual floors of the facility. Transformers complemented by static transfer switches close to the IT equipment can be used to create an isolated redundant backup line with two alternative power-supply paths to the loads. [1]

MV UPSs May Underlie All Future Large-Scale Critical Applications

Increasing power density and total power demand at single sites, combined with rising requirements for high-reliability power in IT, business and production facilities, are today’s trends. The power-supply system has to respond with suitable UPS and distribution designs. High-power, low-voltage systems lead to current limitation in the distribution and, often, must bridge long distances, but the step to a medium voltage level is a suitable technical solution. MV systems reduce cable size and losses, increasing the efficiency of the distribution network. Additionally, the utilization of integrated high-power MV UPS systems can reduce the number of components, such as switch gear and cabling. Basic parts of modern static MV UPSs, including the power electronics and energy storage, come from standard and proven low-voltage equipment, including the power electronics and energy storage. The MV UPS enables a clearly laid-out high-power system configuration, keeping its complexity manageable.

Products like ABB’s PCS100 MV UPS are available in multi-megawatt ratings and enable tailored solutions to large IT, business and mega data centers. Such products should be designed to provide clean, reliable and efficient power at a lower total cost for customers consuming high levels of power. By offering modular features, a modern UPS gives customers an advantage in that they need not invest as much money at the start, allowing them to be flexible in expanding their infrastructure as there business grows. Finally, a single-conversion topology is a natural choice for medium voltage, as losses are extremely small, meaning efficiencies well in excess of 99% are achievable.

References

[1] Frank Herbener, Iso-Parallel UPS Configuration

About the Author

Perry Field is General Manager for Power Conditioning at ABB. Perry studied electrical engineering at the University of Canterbury, New Zealand, gaining bachelor’s and master’s degrees specializing in power electronics. He has worked as an R&D design engineer for variable-speed motor drives before joining Vectek Electronics, designing power-quality and marine converters. For the last four years, Perry has led the product-management team before becoming the general manager for ABB Power Conditioning. For more information, contact mailto:powerconditioning@abb.com or visit ABB’s Medium Voltage UPS page.

Data center designers are increasingly adopting the maxim that bigger is better. Driven to a large extent by the shift toward colocation, hyper-scale data centers are becoming more common. As these facilities have grown larger, they have also grown more generic and their product more of a commodity business.

Today, data-buying decisions, once the required availability level is defined, basically come down to price, and the prime target in driving that price as low as possible is energy. Considering the amount of power consumed, and the fact that energy is typically the largest controllable cost, data center managers are eager to squeeze every possible percent out of their electricity cost.

Energy Efficiency

Eco-mode is a UPS energy-saving feature whereby the load is supplied via a static bypass line. In the past, this solution has mostly gone unused because the cost-benefit equation has been insufficient to warrant the increased risk. A normal double-conversion UPS converts the input AC to DC. The batteries are connected to the DC source to provide continuous charging, and then the DC is inverted back to AC to power the servers. Power loss occurs during those conversions. In eco-mode, the bypass path connects the input AC directly to the output AC.

“There are several reasons operators are more likely to use eco-mode today,” said Perry Field, General Manager for ABB Power Conditioning. “First is improved technology both in the UPS and in the servers they power. UPS technology has improved to a level where operators are more confident that, during a power event, the UPS will transparently compensate. On the server side, the built-in ride-through capability is well proven, reducing operator concerns about protecting power-related events.”

Another factor is that power outages are less frequent in the typical hyper-center than in smaller facilities. Larger facilities tend to be connected to transmission-level mains, where long outages are infrequent.

In the past, the 1–2% energy savings delivered by eco-mode was not worth the risk. But technology enhancements have improved the risk profile and, in the ultra-competitive hyper-center market, saving 1% in energy costs provides a desirable cost advantage.

Reusable Energy

Often there is more talk than action in the area of reusable and renewable energy, but there is little doubt that both will become increasingly important sources of increased efficiency and reliability in the years ahead. Here, the mantra of “reduce, reuse, recycle” may be appropriate.

Various strategies are under consideration to reduce the heat generated in a data center. One is the use of DC voltage to power servers. The AC-to-DC transformer in each server is a major heat generator, but by eliminating the transformer, you can greatly reduce the heat.

Widespread adoption of this approach is unlikely in the short term. In the meantime, operators are looking for ways to reuse and recycle that heat.

Although some data center construction occurs in relatively remote areas to take advantage of low land/space costs, other projects take the opposite approach, locating their centers in urban areas. In this scenario, the heat generated from the servers can warm adjacent buildings. These facilities also have the benefit of proximity to major data trunks.

Renewable Energy

Many data center operators are closely investigating renewable energy. This option offers the potential for lower-cost energy and provides an alternative to the grid in areas where reliability is an issue. Of course, renewables have their own reliability issues. The wind may not blow and the sun may not shine, or they may do so at times when power is not really needed.

“To realize the benefits of renewables while overcoming their limitations,” Perry explains, “data centers can rely on a microgrid approach that combines multiple resources such as the grid, diesel generation, and renewables. It is no simple task but it is being done successfully, mainly in remote communities or industrial facilities where grid-delivered power is particularly expensive or unreliable.”

Technology is available today to successfully address issues related to the shifting power flows that occur in microgrids. Energy-storage converters can deliver power when needed and absorb power when the renewables produce more than is currently required.

“Because of the complexity of microgrids, most data centers are better off simply identifying a low-cost power source from the local utility,” Perry observes. “However, in places where there are constraints on power sources or that do not have access to reliable electricity, people are seriously investigating these alternatives. As technology evolves to further simplify microgrid management, you will see data centers increasingly embrace the concept.”

More Medium Voltage

Technology does not always scale well. The low-voltage (<480 V) systems used in data centers are a good example. Enterprise-scale centers are well suited to using low voltage. As centers grow, though, the drawbacks of low voltage begin to add inefficiency and increase both capital and operations costs.

The capital costs of a low-voltage system are higher because they require large conductors, big switchboards and multiple circuit breakers. Maintaining all these devices increases ongoing maintenance costs. Medium-voltage systems, on the other hand, provide a more central approach. Although a low-voltage system may have 10 UPS units at a lower power rating, a medium-voltage system may have only 2 or 3.

“As the current in a medium-voltage system is lower, the efficiency of the whole system is extremely high. The comfort level that operators have with traditional, low-voltage systems means that adoption of medium-voltage topology is likely to be cautiously slow. As industry leaders begin to make the transition, however, the move to medium voltage is a trend that we expect will accelerate.”

Medium-voltage systems will provide benefits in very large data centers, but the benefits can extend down to smaller installations in the 5–10 MW range as well.

Tracking Trends

In many industries, predicting trends is difficult. But in the data center market, some trends are easily identified. One example is that for the foreseeable future, more processing will be done in hyper-centers, and these massive warehouses of computing power will relentlessly seek solutions that reduce costs and deliver price advantages. Increased energy efficiency through new technology, including more-advanced UPS systems and medium-voltage topology, is a promising path to greater efficiency.

“Manufacturers will continue to respond to customer demand for further technology improvements, leading to even greater enhancements in energy efficiency and power quality,” Perry predicts. “Technology advancements combined with the willingness of data center operators to explore new approaches to energy management will drive continued operational innovation and efficiency.”

About the Author

John Mousaw is Director of Global Communications for ABB’s data center business, which includes a broad portfolio of integrated solutions, products and services, from power-distribution systems to enterprise management and grid connections. ABB is a global leader in power and automation operates in around 100 countries and employs about 145,000 people. The company is holding a Data Center Day at APW on March 2, 2015, in Houston, Texas. For more information, contact powerconditioning@abb.com.

The importance of a stable uninterrupted power system (UPS) is one that should never be downplayed—with a misguided spark, even the shortest of power outages could spell big trouble for the most established structures.

As the industry turns its attention to power-outage cases, the need for regular UPS maintenance regimes and apt data center solutions is being amplified. What this situation illustrates is that not only can companies ill afford to leave their IT assets unprotected from power issues, but all corporations—big and small—are equally susceptible to these problems.

As we continue to learn from experience, it is apparent that power sags, surges and outages are not only unavoidable but also more than capable of damaging valuable IT equipment and bringing productivity to a halt. And although backups are a given, it is imperative to have a good understanding of the systems involved and to plan and deploy a robust power-protection solution.

Which UPS Is Right for the Job?

Think of the UPS as the central component of any well-designed power protection architecture; put simply, a UPS is a device that provides backup power when utility power fails, either long enough for critical equipment to shut down gracefully so that no data is lost, or long enough to keep required loads operational until a generator comes online.

The majority of data centers today are using static UPS systems. They typically consist of banks of lead-acid batteries that store energy to provide line conditioning and backup to network equipment during power disturbances. If the disturbance progresses to an outage, diesel-fueled power generators are switched on. Static UPS systems provide load isolation, are relatively straightforward to maintain and can provide a range of ride-through times using different battery string configuration/sizes when utility power goes down.

Another type of UPS is the rotary UPS, which uses a motor/generator to create output. Rotary UPSs can provide high fault-clearing capabilities (peak/maximum current to blow a fuse) without going to bypass. Thus, the unit is able to provide “short-circuit current” to blow a fuse or trip a protection switch downstream instead of “protecting itself” as static UPSs do. In terms of maintainability, rotary UPSs require periodic downtime for mechanical maintenance, whereas static UPSs may not if batteries can be hot-swapped.

With so much to consider, mission-critical facilities would thus have to select the most ideal UPS and also learn to tweak the systems to fit their usage and needs.

Health Check Your Power System

Although choosing the right UPS is crucial for any application, a wellness check for the power system is equally vital. A well-managed power system is the foundation of any successful enterprise, delivering reliability, efficiency and safety. But as an organization grows, demands on the power system increase, necessitating equipment additions or replacements.

Over time, the power system evolves into a disparate collection of equipment that doesn’t always deliver the desired results. Eventually, it can become more complicated, inefficient and harder to manage as expectations for performance rise. That’s why a holistic and preventative approach is essential for the evaluation of the system’s health.

A comprehensive power-management audit can address such issues and consists of visual inspections, electrical measurements, interviews with onsite personnel, and reviews of utility bills and data. Specifically, it will analyze interruptions, voltage sags, harmonics, surge protection, grounding, energy management and arc-flash safety. The audit will also evaluate the present state of the existing safety guidelines, including the use of personal protective equipment, and offer recommendations for improvement.

Based on an Electric Power Research Institute study, the U.S. economy is losing between $104 billion and $164 billion to outages, and another $15 billion to $24 billion to power-quality phenomena.1 Nearly 80% of power disturbances that interrupt business occur because of problems in the facility itself.2 So, what else can be done?

How to Prevent a Standstill

Companies should still continue ensuring quality upkeep of their UPSs for data center backups, but they must also ensure that they have performed regular preventative maintenance for the entire data center system.

Preventive maintenance is crucial to achieving optimal equipment performance. Systematic inspections, testing and cleaning by trained technicians ensure the various electronic and mechanical components of a UPS are functioning to maximum potential. When problems are detected and repaired before they evolve into significant—and often costly—issues, UPSs will be able to deliver the level of expected performance. Preventive maintenance is also crucial to achieving maximum performance from equipment by affording the opportunity to detect and repair potential problems.

No company can afford to leave its IT assets unprotected from power issues. This is because even short power fluctuations, as little as a quarter second, can trigger events that may keep IT equipment unavailable for anywhere from 15 minutes to hours. Utility power is also less than 100% reliable. In fact, it is only 99.9% reliable in the U.S., which translates into a likely nine hours of utility outages every year.

As availability is the critical to success these days, core business processes can quickly come to a standstill if IT systems go down, meaning companies would eventually lose out to their competitors if their data centers are not kept in check.

Highly efficient UPS systems can not only help in providing reliable backup power to data centers, but they also allow companies to better manage costs. Considering how the cost of power and cooling has spiraled upward in recent years, cost savings are essential. Data center managers are typically held responsible for achieving high availability while simultaneously reducing power costs—a seemingly impossible feat amidst rising costs. Not all is lost, however, as highly efficient UPS systems can help them achieve this balance and attain their goals.

So if you are questioning whether to take the next step in your power protection regime, it’s probably high time to do so—before a problem arises.

[1] The Cost of Power Disturbances to Industrial & Digital Economy Companies. Electric Power Research Institute, 2001

About the Author

Teng Seen Khoo is VP of sales for Eaton’s electrical business in East Asia. Eaton was recently awarded the Southeast Asia UPS Industry Product Line Strategy Leadership award in the 2014 Frost & Sullivan Asia Pacific Best Practices Awards. The awards recognize companies that have implemented best practices in their industry, as well as demonstrated excellent achievements and superior performance in areas such as leadership, technological innovation and strategic product and service development.

The tendency towards mega data centers in the internet and IT sectors requires an increasing demand for stable power at single locations. With more demand for data storage (owing to frequent uploads of photos to Facebook or other social-media accounts), data centers are becoming bigger and consuming larger amounts of power. They are beginning to take on a more industrial approach to power consumption. That said, more and more large, critical industrial processes rely on a power-quality level that the public grid cannot provide. The distribution of the electrical power in many of these large facilities is realized at medium-voltage (MV) level.

Medium-voltage distribution reduces losses and space by a simple reduction in current. As voltages increase, the required current reduces for the same power level. The modular design of a static UPS allows a simple replacement of the grid-to-load interface from low-voltage (LV) to medium-voltage components, keeping the basic parts of the UPS and storage the same as for LV applications. In this way, the proven and familiar experience of working with the function and maintainability of a reliable LV UPS is maintained, but the advantages of medium voltage are achieved.

Advantages of Medium-Voltage UPS Technology

Fast-growing online activity over the last decade has forced a rapid rise in both space and electrical power required to operate data centers. Accordingly, power density becomes higher, and cooling of these data centers becomes critical. Economies of scale mean single data center locations have grown larger, with a demand for a safe power supply reaching well into the tens of megawatts. Integrating a medium-voltage UPS system to protect these critical applications will reduce feeder ampacity. For example, 1 MW in a 400/230 VAC system means 1,443 A of current per phase. If the voltage is 15 kV, the current for 1 MW power is only 115 A. Another feature of the MV UPS is that the system can be centralized, which helps manage floor loading and gives freedom in the floor plan.

One of the major cost issues in a data center or a production facility is efficient use of floor space. Reducing the space for infrastructure equipment results in additional space for IT or manufacturing equipment. Often the available area for the UPS system is limited, particularly in existing buildings, but the required power is increasing. High-power, compact, MV static UPS products are well suited to overcoming this challenge. Modern static MV UPS systems also make extensive use of low-voltage components, including the entire power-electronics, energy-storage and control systems taken from standard and proven low-voltage units.

Besides the footprint, electrical losses are an important point to consider. Particularly at long distribution distances, distribution losses can become significant. For longer distribution lengths, the influence of the cable will rise, so medium voltage will yield a better result.

Typical MV Applications Now Appear in Today’s Economy

In mega data centers, the philosophy is quite similar. Many design options are possible, including performing the UPS function at medium voltage and having MV distributed to the individual floors of the facility. Transformers complemented by static transfer switches close to the IT equipment can be used to create an isolated redundant backup line with two alternative power-supply paths to the loads. [1]

MV UPSs May Underlie All Future Large-Scale Critical Applications

Increasing power density and total power demand at single sites, combined with rising requirements for high-reliability power in IT, business and production facilities, are today’s trends. The power-supply system has to respond with suitable UPS and distribution designs. High-power, low-voltage systems lead to current limitation in the distribution and, often, must bridge long distances, but the step to a medium voltage level is a suitable technical solution. MV systems reduce cable size and losses, increasing the efficiency of the distribution network. Additionally, the utilization of integrated high-power MV UPS systems can reduce the number of components, such as switch gear and cabling. Basic parts of modern static MV UPSs, including the power electronics and energy storage, come from standard and proven low-voltage equipment, including the power electronics and energy storage. The MV UPS enables a clearly laid-out high-power system configuration, keeping its complexity manageable.

Products like ABB’s PCS100 MV UPS are available in multi-megawatt ratings and enable tailored solutions to large IT, business and mega data centers. Such products should be designed to provide clean, reliable and efficient power at a lower total cost for customers consuming high levels of power. By offering modular features, a modern UPS gives customers an advantage in that they need not invest as much money at the start, allowing them to be flexible in expanding their infrastructure as there business grows. Finally, a single-conversion topology is a natural choice for medium voltage, as losses are extremely small, meaning efficiencies well in excess of 99% are achievable.

References

[1] Frank Herbener, Iso-Parallel UPS Configuration

About the Author

Perry Field is General Manager for Power Conditioning at ABB. Perry studied electrical engineering at the University of Canterbury, New Zealand, gaining bachelor’s and master’s degrees specializing in power electronics. He has worked as an R&D design engineer for variable-speed motor drives before joining Vectek Electronics, designing power-quality and marine converters. For the last four years, Perry has led the product-management team before becoming the general manager for ABB Power Conditioning. For more information, contact mailto:powerconditioning@abb.com or visit ABB’s Medium Voltage UPS page.

Data center designers are increasingly adopting the maxim that bigger is better. Driven to a large extent by the shift toward colocation, hyper-scale data centers are becoming more common. As these facilities have grown larger, they have also grown more generic and their product more of a commodity business.

Today, data-buying decisions, once the required availability level is defined, basically come down to price, and the prime target in driving that price as low as possible is energy. Considering the amount of power consumed, and the fact that energy is typically the largest controllable cost, data center managers are eager to squeeze every possible percent out of their electricity cost.

Energy Efficiency

Eco-mode is a UPS energy-saving feature whereby the load is supplied via a static bypass line. In the past, this solution has mostly gone unused because the cost-benefit equation has been insufficient to warrant the increased risk. A normal double-conversion UPS converts the input AC to DC. The batteries are connected to the DC source to provide continuous charging, and then the DC is inverted back to AC to power the servers. Power loss occurs during those conversions. In eco-mode, the bypass path connects the input AC directly to the output AC.

“There are several reasons operators are more likely to use eco-mode today,” said Perry Field, General Manager for ABB Power Conditioning. “First is improved technology both in the UPS and in the servers they power. UPS technology has improved to a level where operators are more confident that, during a power event, the UPS will transparently compensate. On the server side, the built-in ride-through capability is well proven, reducing operator concerns about protecting power-related events.”

Another factor is that power outages are less frequent in the typical hyper-center than in smaller facilities. Larger facilities tend to be connected to transmission-level mains, where long outages are infrequent.

In the past, the 1–2% energy savings delivered by eco-mode was not worth the risk. But technology enhancements have improved the risk profile and, in the ultra-competitive hyper-center market, saving 1% in energy costs provides a desirable cost advantage.

Reusable Energy

Often there is more talk than action in the area of reusable and renewable energy, but there is little doubt that both will become increasingly important sources of increased efficiency and reliability in the years ahead. Here, the mantra of “reduce, reuse, recycle” may be appropriate.

Various strategies are under consideration to reduce the heat generated in a data center. One is the use of DC voltage to power servers. The AC-to-DC transformer in each server is a major heat generator, but by eliminating the transformer, you can greatly reduce the heat.

Widespread adoption of this approach is unlikely in the short term. In the meantime, operators are looking for ways to reuse and recycle that heat.

Although some data center construction occurs in relatively remote areas to take advantage of low land/space costs, other projects take the opposite approach, locating their centers in urban areas. In this scenario, the heat generated from the servers can warm adjacent buildings. These facilities also have the benefit of proximity to major data trunks.

Renewable Energy

Many data center operators are closely investigating renewable energy. This option offers the potential for lower-cost energy and provides an alternative to the grid in areas where reliability is an issue. Of course, renewables have their own reliability issues. The wind may not blow and the sun may not shine, or they may do so at times when power is not really needed.

“To realize the benefits of renewables while overcoming their limitations,” Perry explains, “data centers can rely on a microgrid approach that combines multiple resources such as the grid, diesel generation, and renewables. It is no simple task but it is being done successfully, mainly in remote communities or industrial facilities where grid-delivered power is particularly expensive or unreliable.”

Technology is available today to successfully address issues related to the shifting power flows that occur in microgrids. Energy-storage converters can deliver power when needed and absorb power when the renewables produce more than is currently required.

“Because of the complexity of microgrids, most data centers are better off simply identifying a low-cost power source from the local utility,” Perry observes. “However, in places where there are constraints on power sources or that do not have access to reliable electricity, people are seriously investigating these alternatives. As technology evolves to further simplify microgrid management, you will see data centers increasingly embrace the concept.”

More Medium Voltage

Technology does not always scale well. The low-voltage (<480 V) systems used in data centers are a good example. Enterprise-scale centers are well suited to using low voltage. As centers grow, though, the drawbacks of low voltage begin to add inefficiency and increase both capital and operations costs.

The capital costs of a low-voltage system are higher because they require large conductors, big switchboards and multiple circuit breakers. Maintaining all these devices increases ongoing maintenance costs. Medium-voltage systems, on the other hand, provide a more central approach. Although a low-voltage system may have 10 UPS units at a lower power rating, a medium-voltage system may have only 2 or 3.

“As the current in a medium-voltage system is lower, the efficiency of the whole system is extremely high. The comfort level that operators have with traditional, low-voltage systems means that adoption of medium-voltage topology is likely to be cautiously slow. As industry leaders begin to make the transition, however, the move to medium voltage is a trend that we expect will accelerate.”

Medium-voltage systems will provide benefits in very large data centers, but the benefits can extend down to smaller installations in the 5–10 MW range as well.

Tracking Trends

In many industries, predicting trends is difficult. But in the data center market, some trends are easily identified. One example is that for the foreseeable future, more processing will be done in hyper-centers, and these massive warehouses of computing power will relentlessly seek solutions that reduce costs and deliver price advantages. Increased energy efficiency through new technology, including more-advanced UPS systems and medium-voltage topology, is a promising path to greater efficiency.

“Manufacturers will continue to respond to customer demand for further technology improvements, leading to even greater enhancements in energy efficiency and power quality,” Perry predicts. “Technology advancements combined with the willingness of data center operators to explore new approaches to energy management will drive continued operational innovation and efficiency.”

About the Author

John Mousaw is Director of Global Communications for ABB’s data center business, which includes a broad portfolio of integrated solutions, products and services, from power-distribution systems to enterprise management and grid connections. ABB is a global leader in power and automation operates in around 100 countries and employs about 145,000 people.

The importance of a stable uninterrupted power system (UPS) is one that should never be downplayed—with a misguided spark, even the shortest of power outages could spell big trouble for the most established structures.

As the industry turns its attention to power-outage cases, the need for regular UPS maintenance regimes and apt data center solutions is being amplified. What this situation illustrates is that not only can companies ill afford to leave their IT assets unprotected from power issues, but all corporations—big and small—are equally susceptible to these problems.

As we continue to learn from experience, it is apparent that power sags, surges and outages are not only unavoidable but also more than capable of damaging valuable IT equipment and bringing productivity to a halt. And although backups are a given, it is imperative to have a good understanding of the systems involved and to plan and deploy a robust power-protection solution.

Which UPS Is Right for the Job?

Think of the UPS as the central component of any well-designed power protection architecture; put simply, a UPS is a device that provides backup power when utility power fails, either long enough for critical equipment to shut down gracefully so that no data is lost, or long enough to keep required loads operational until a generator comes online.

The majority of data centers today are using static UPS systems. They typically consist of banks of lead-acid batteries that store energy to provide line conditioning and backup to network equipment during power disturbances. If the disturbance progresses to an outage, diesel-fueled power generators are switched on. Static UPS systems provide load isolation, are relatively straightforward to maintain and can provide a range of ride-through times using different battery string configuration/sizes when utility power goes down.

Another type of UPS is the rotary UPS, which uses a motor/generator to create output. Rotary UPSs can provide high fault-clearing capabilities (peak/maximum current to blow a fuse) without going to bypass. Thus, the unit is able to provide “short-circuit current” to blow a fuse or trip a protection switch downstream instead of “protecting itself” as static UPSs do. In terms of maintainability, rotary UPSs require periodic downtime for mechanical maintenance, whereas static UPSs may not if batteries can be hot-swapped.

With so much to consider, mission-critical facilities would thus have to select the most ideal UPS and also learn to tweak the systems to fit their usage and needs.

Health Check Your Power System

Although choosing the right UPS is crucial for any application, a wellness check for the power system is equally vital. A well-managed power system is the foundation of any successful enterprise, delivering reliability, efficiency and safety. But as an organization grows, demands on the power system increase, necessitating equipment additions or replacements.

Over time, the power system evolves into a disparate collection of equipment that doesn’t always deliver the desired results. Eventually, it can become more complicated, inefficient and harder to manage as expectations for performance rise. That’s why a holistic and preventative approach is essential for the evaluation of the system’s health.

A comprehensive power-management audit can address such issues and consists of visual inspections, electrical measurements, interviews with onsite personnel, and reviews of utility bills and data. Specifically, it will analyze interruptions, voltage sags, harmonics, surge protection, grounding, energy management and arc-flash safety. The audit will also evaluate the present state of the existing safety guidelines, including the use of personal protective equipment, and offer recommendations for improvement.

Based on an Electric Power Research Institute study, the U.S. economy is losing between $104 billion and $164 billion to outages, and another $15 billion to $24 billion to power-quality phenomena.1 Nearly 80% of power disturbances that interrupt business occur because of problems in the facility itself.2 So, what else can be done?

How to Prevent a Standstill

Companies should still continue ensuring quality upkeep of their UPSs for data center backups, but they must also ensure that they have performed regular preventative maintenance for the entire data center system.

Preventive maintenance is crucial to achieving optimal equipment performance. Systematic inspections, testing and cleaning by trained technicians ensure the various electronic and mechanical components of a UPS are functioning to maximum potential. When problems are detected and repaired before they evolve into significant—and often costly—issues, UPSs will be able to deliver the level of expected performance. Preventive maintenance is also crucial to achieving maximum performance from equipment by affording the opportunity to detect and repair potential problems.

No company can afford to leave its IT assets unprotected from power issues. This is because even short power fluctuations, as little as a quarter second, can trigger events that may keep IT equipment unavailable for anywhere from 15 minutes to hours. Utility power is also less than 100% reliable. In fact, it is only 99.9% reliable in the U.S., which translates into a likely nine hours of utility outages every year.

As availability is the critical to success these days, core business processes can quickly come to a standstill if IT systems go down, meaning companies would eventually lose out to their competitors if their data centers are not kept in check.

Highly efficient UPS systems can not only help in providing reliable backup power to data centers, but they also allow companies to better manage costs. Considering how the cost of power and cooling has spiraled upward in recent years, cost savings are essential. Data center managers are typically held responsible for achieving high availability while simultaneously reducing power costs—a seemingly impossible feat amidst rising costs. Not all is lost, however, as highly efficient UPS systems can help them achieve this balance and attain their goals.

So if you are questioning whether to take the next step in your power protection regime, it’s probably high time to do so—before a problem arises.

[1] The Cost of Power Disturbances to Industrial & Digital Economy Companies. Electric Power Research Institute, 2001

About the Author

Teng Seen Khoo is VP of sales for Eaton’s electrical business in East Asia. Eaton was recently awarded the Southeast Asia UPS Industry Product Line Strategy Leadership award in the 2014 Frost & Sullivan Asia Pacific Best Practices Awards. The awards recognize companies that have implemented best practices in their industry, as well as demonstrated excellent achievements and superior performance in areas such as leadership, technological innovation and strategic product and service development.

Industry Outlook is a regular Data Center Journal Q&A series that presents expert views on market trends, technologies and other issues relevant to data centers and IT.

This week, Industry Outlook asks Mark A. Ascolese about flywheel UPS products and their potential value to data centers. Mark was named president and CEO of Active Power in September 2013. He is an electrical-infrastructure and energy-management expert with more than 40 years of experience serving a variety of mission-critical and energy markets including data centers. Before joining Active Power, Mark first served as CEO and then as board chairman of Power Analytics, an electrical-infrastructure enterprise software firm. He has also served in senior-level management positions at Powerware (now part of Eaton Corp.) and General Electric. From 2000–2002, he was senior vice president of business development at Active Power during the company’s initial public offering. In this role, Mark led the effort in securing multimillion-dollar distribution and development agreements with key market players. He earned a bachelor of science in commerce from the University of Louisville.

Industry Outlook: What prompted you to return to Active Power in October 2014 after having served as the company’s senior vice president of business development from 2000–2002?

Mark A. Ascolese: I’ve always felt the technology at Active Power is elegant and has a unique role to play in the market. The employees here have an unrivaled passion for our technology and our growing marquee customer base, and the company continued to grow during the 12 years I was away, so I saw this as an opportunity with tremendous upside.

IO: What is one aspect of Active Power that customers are surprised about when you tell them?

MAA: Many are surprised to learn Active Power has more than 4,000 flywheels deployed worldwide delivering more than 900 megawatts of critical power protection. This is a technology that is mature, field proven and trusted by some of the most visible brands in the world to protect their mission-critical operations. I believe many would also find it surprising the data center market represents less than half of our installed base

IO: Having been in the electrical infrastructure space for more than 40 years, how do you see the landscape of UPS suppliers evolving, if at all?

MAA: Many suppliers, especially the larger companies, are apprehensive toward change. Rather than develop and bring new technologies to market, they are simply expanding through the acquisition of existing technologies and successful smaller companies. I believe this mindset bodes well for companies like Active Power that have taken the time to examine customers’ needs and are providing highly efficient and environmentally friendly products and solutions.

IO: Who is the ideal customer for a flywheel UPS?

MAA: Customer needs vary depending on the market segment and application, but the ideal customer, especially in the data center space, is open to fresh, forward-thinking approaches to electrical design that will make their facility less wasteful and more efficient. We work with sophisticated customers who are focused on improving reliability and efficiency, reducing total cost of ownership and enhancing environmental sustainability.

During a recent trip to Europe, I visited a number of our larger installations, and in each case the customer was very complimentary of the reliability of these UPS solutions, the significant impact the product has on reducing their operating costs and the pride they have in minimizing their environmental impact.

IO: With all the advantages of flywheel UPSs, why are operators still hesitant to deploy these types of systems?

MAA: The mission-critical market and the various constituents that support it are risk averse, particularly in terms of electrical-infrastructure design. It is the old axiom that no one ever got fired for buying IBM. The purchase and installation of a legacy technology that has been used for more than 50 years is viewed by some as easier and safer than investing in emerging technologies like flywheels.

I believe this risk aversion, in part, leads to inefficient power designs that don’t meet the needs of today’s mission-critical operations. We need to break this paradigm. We have to work smarter and better articulate our value proposition that ultimately delivers more-creative system designs that better serve our customers’ needs.

IO: What are common trends you’re seeing in electrical infrastructure design?

MAA: We are seeing a move toward shorter run times in UPS equipment—down to two minutes or less—which is due in part to the advent of cloud computing and virtualization that enables greater resiliency. This trend is driven by the desire to reduce capital and operating cost, achieve maximum energy efficiency and reduce the use of harmful materials and chemicals. These are all strong selling points for us, as our systems operate at efficiencies of up to 98% and do not use harmful materials like lead.

MAA: A key concern for all data centers should be the environmental impact of their facility. As a data center operator for a major university in the United States told me recently, “There is no technical reason that justifies anyone deploying environmentally harmful materials in data center UPS systems today.” By investing in flywheel UPS technologies, they can eliminate batteries and still operate at high efficiencies.

IO: How are IT trends affecting the UPS market?

MAA: For decades, organizations have been driving IT resiliency through hardware redundancy and a culture of no tolerance for failure. These trends drive high capital and operating costs in critical power infrastructure that are unnecessary, particularly in today’s data center. This excess redundancy causes a significant impact in equipment underutilization. To address this problem, cloud computing and virtualization are becoming more commonplace, which is driving down the need for long ride-through times in UPS equipment.

IO: How has a sluggish economy affected the UPS business?

MAA: Obviously, a slower economy translates into fewer opportunities. There is evidence that the sluggish economy has resulted in a slowdown in demand for compute power resulting in an oversupply of data center capacity. It will take some time for that oversupply to be absorbed. That said, the latest UPS market data forecast a recovery for larger UPS systems in 2015, with growth being greatest in colocation, cloud and IT services.

IO: Where do you see the modular data center market going over the next two to three years?

MAA: The benefits of modular data center design are clear: capital preservation, speed to deployment and operational efficiencies. A modular approach can provide IT and/or associated power and cooling infrastructure when cost, time and space constraints exist. In the past, lots of options and a diluted value proposition confused customers, leading to indifference over the entire idea of modular. I see this approach as an opportunity for suppliers to simplify their products and positioning and to return to the simple, inexpensive concepts at the heart of modular design.